1. Field of the Invention
This invention relates to a non-linear coder for use in a time-division multiplex pulse code modulation telephone transmission system and the like.
2. Description of the Prior Art
Conventional non-linear coding systems for use in telephone transmission are generally based on digital companding. Those are exemplified by the so-called "A-law" or ".mu.-law", each having a companding matrix in the feedback loop thereof. An example of such non-linear coding systems is shown in U.S. Pat. No. 3,676,600 to Kaneko et al. Although feedback type coders are widely used because of their simplicity in construction, they have an inherent problem of loop delay time which is the composite delay time inherent to the circuit forming the feedback loop of the feedback type coder. This affects the coding period, that is, the time period from coding of a certain particular bit to coding of the subsequent bit. A high speed coder must have a short coding period, so that high speed operations are required for the respective circuits forming the feedback loop. The coding speed is limited mainly by the companding matrix used in the feedback loop.